The present invention is directed generally to a fiber optic device, and more particularly to a fiber optic device that operates at two wavelengths.
Optical fibers find many uses for directing beams of light between two points. Optical fibers have been developed to have low loss, low dispersion, and polarization maintaining properties and can also act as amplifiers. As a result, optical fiber systems find widespread use, for example in optical communication applications.
However, one of the important advantages of fiber optic beam transport, that of enclosing the optical beam within a fiber to guide it between terminal points, is also a limitation. Many types of optical device need to be included in a fiber optic system to control or otherwise regulate the flow of light from one point to another, such as filters, optical switches, circulators, and the like. Many of these devices are typically implemented in a bulk form, rather than in a waveguide form, requiring that the light must freely propagate through the device. Consequently, the inclusion of an optical device necessitates that the optical fiber system have a section where the beam path propagates freely in space, rather than being guided within a fiber.
Furthermore, it is not uncommon to find that an optical fiber supports the transport of light at two or more wavelengths. For example, the communications signal propagating along the fiber may have a wavelength of about 1.55 xcexcm, while a diagnostic signal may also be sent along the fiber, having a wavelength of approximately 1.3 xcexcm. Other wavelengths that may be used. in the same fiber as the communications signal include a pump signal for pumping an optical amplifier. For example, where the optical signal is at about 1.55 xcexcm, the pump signal may be at about 980 nm for pumping an erbium-doped fiber amplifier, or at about 1.48 xcexcm for pumping a fiber Raman amplifier. It is common that an optical device be inserted in an optical fiber system to operate on light at only one of the wavelengths present. It may also be the case that different operations have to be applied to light at different wavelengths.
Accordingly, there is a need for fiber optic devices that can operate in fiber-based systems that have light propagating within the fiber at more than one wavelength.
Generally, the present invention relates to a device for use in fiber optic systems that operate with light at more than one wavelength. The device may be inserted anywhere within the fiber network. One particular embodiment of the invention permits the separation of the wavelengths so that an optical device can operate on that separated wavelength without operating on the other wavelength or wavelengths. The different wavelengths may then be recombined. In another embodiment of the invention, different wavelengths may be combined into a single fiber, with an optical device being disposed to operate on one of the wavelengths.
One particular embodiment of the invention is a fiber optic device that includes a first optical fiber optically coupled to transmit light at first and second wavelengths along a first optical path and a wavelength separator disposed on the first optical path which is adapted to direct light at the first wavelength along a second optical path and light at the second wavelength along a third optical path different from the second optical path. A wavelength combiner is optically coupled to combine light propagating along the second and third optical paths into a fourth optical path and a second optical fiber is optically coupled to the fourth optical path. A first optical device disposed along the second optical path, between the wavelength separator and the wavelength combiner to operate on light at the first wavelength. In different variations, the first optical device may be, for example, an optical modulator, a switch, an optical filter, or a circulator.
In another embodiment of the invention, a fiber optic device includes wavelength splitting means for splitting a light beam into a first light beam containing light at a first wavelength and a second light beam containing light at a second wavelength, the first and second beams respectively propagating along first and second beam paths. A first optical device is disposed on the first beam path to operate on the first light beam. The fiber optic device also includes wavelength combining means for combining light propagating in the first direction along the first beam path, and light propagating in the first direction along the second beam path into a single output beam.
In another embodiment of the invention, first and second optical fibers are optically coupled via first and second optical paths respectively to a wavelength combiner. Light at a first wavelength from the first optical fiber is combined with light at a second wavelength from the second fiber at the wavelength combiner to form a combined output beam. A third optical fiber is coupled via a third optical path to receive the combined output beam from the wavelength combiner. A first optical device is positioned on the first optical path between the first optical fiber and the wavelength combiner.
In another embodiment of the invention, a first optical fiber is optically coupled via a first optical path to a wavelength separator to transmit light to the wavelength separator which is arranged to separate light received from the first optical fiber into components at first and second wavelengths. A second optical fiber is coupled via a second optical path to the wavelength separator to receive light at the first wavelength. A third optical fiber is coupled via a third optical path to the wavelength separator to receive light at the second wavelength, and a first optical device is positioned on the second optical path between the second optical fiber and the wavelength separator.
The above summary of the present invention is not intended to describe each illustrated embodiment or every implementation of the present invention. The figures and the detailed description which follow more particularly exemplify these embodiments.